Satellite and digital cable high definition (HD) television are available in the television industry today. Now, however, telephone companies are improving the technology of Internet Protocol Television (IPTV) to establish IPTV as an alternative that is more desirable than satellite and cable television. Therefore, one goal of IPTV is to competitively offer HD television, and more. Telephone companies contemplate this via “triple play,” a subscriber service of voice, data and video.
One challenge, however, involves a transmission bottleneck due to the narrow “copper pipe” (narrow bandwidth) through that video data must travel in the “last mile” of the path of transmission between a digital television service provider and a subscriber home. Conventionally, the DSLAM (digital subscriber-line access manager) marks the “edge” or beginning of the “last mile” in IPTV. Typically, a wide “fiber optic pipe” having an abundance of bandwidth leads to the DSLAM. In addition, the narrow copper pipe connects the DSLAM to the subscriber premises. Essentially, the copper pipe is the traditional telephone line infrastructure that already exists.
One particular issue with the copper pipe is that it rapidly attenuates video data with distance and therefore the bandwidth of the copper pipe substantially degrades from its peak bit-rate the further the distance from the DSLAM to the subscriber. A subscriber who is too far from the DSLAM has an impaired subscriber-line. An impaired subscriber-line is characterized as having less throughput than the peak bit-rate of whatever physical medium transmission technology is used to convey data across the physical medium. A subscriber who requests too much bandwidth creates a congested-state subscriber-line. A congested-state subscriber-line is characterized as having less throughput than bandwidth requested by the subscriber.
Typically in IPTV, a channel is not forwarded from the DSLAM to the subscriber unless a subscriber has specifically requested to view the channel. In this, consider three scenarios involving a second person requesting to view a second channel when a first viewer is already viewing a first channel.
In the first scenario, note, an HD channel is 8 Mbps and an SD (standard definition) channel is 4 Mbps. The copper pipe between the DSLAM and a particular subscriber premises is characterized as having a bandwidth of 12 Mbps in total. One viewer at the subscriber premises is watching a television program on an HD channel (8 Mbps). Another viewer at the same subscriber premises, using a different television, then attempts to watch a different program on an SD channel (4 Mbps). Because the bandwidth requested is 12 Mbps in total (8 Mbps+4 Mbps=12 Mbps), both viewers have a positive experience of watching the television programming each requested to watch.
In the second scenario, nearly all circumstances are the same except the subscriber-line is an impaired line having available bandwidth of only 11 Mbps in total. In this second scenario, the subscriber premises is further from the DSLAM when compared to the subscriber premises in the first scenario, and thus there is less bandwidth available. The first viewer is watching one SD channel (4 Mbps) and the second viewer requests one HD channel (8 Mbps). Here, the question is: what is the desired outcome? If the system grants priority to the most recent request of the second viewer and entirely shuts down service to the first viewer due to insufficient bandwidth, then it is likely that the first viewer will be unhappy. Further, the consequence of denial is 3 Mbps of unused bandwidth in total (11 Mbps−8 Mbps=3 Mbps).
In the third scenario, there is also an impaired subscriber-line having available only 11 Mbps of bandwidth in total. The first viewer is watching one HD channel (8 Mbps) and the second viewer requests one SD channel (4 Mbps). Here, again, the question is: what is the desired outcome? If the system grants priority to the more recent request of the second viewer and entirely shuts down service to the first viewer due to insufficient bandwidth, then it is likely the first person will be unhappy. Perhaps the first person will be particularly unhappy to know that the consequence of denial is 7 Mbps of unused bandwidth in total (11 Mbps−4 Mbps=7 Mbps). Not to mention, the service provider will also be unhappy that 7 Mbps of available bandwidth are unused.
It would therefore be beneficial to have a system that cost effectively maximizes the available bandwidth and minimizes degradation and disruption to viewing experience in situations involving requests for more video data than can actually fit through the pipe.